Obscuring, color matching, and camouflaging solar panels

ABSTRACT

A solar panel includes a plurality of photovoltaic cells embedded in a layer of encapsulant. A textured and/or colored layer is positioned on a back side of the layer of encapsulant. The textured and/or colored layer matches a color and/or texture of the plurality of photovoltaic cells. A top layer is positioned on a front side of the layer of encapsulant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/796,683, titled “Obscuring, Color Matching, and Camouflaging SolarPanels,” filed Oct. 27, 2017, which claims priority to the followingU.S. provisional patent applications: U.S. provisional patentapplication No. 62/414,275, titled “Obscuring Solar Arrays From CertainViewing Angles,” filed on Oct. 28, 2016; U.S. provisional patentapplication No. 62/450,000, titled “Coated Backsheet for Solar Panels,”filed Jan. 24, 2017; U.S. provisional patent application No. 62/452,221,titled “Solar Cell Camouflage Structures,” filed Jan. 30, 2017; and U.S.provisional patent application No. 62/452,269, titled “Solar CellCamouflage Structures,” filed Jan. 30, 2017, the content of each ofthese applications is hereby incorporated by reference in its entiretyfor all purposes

BACKGROUND Technical Field

The present disclosure relates to solar panels; and more particularly totechniques for obscuring solar panels from certain sight lines orvantage points, color matching a backsheet of a solar panel with thecell of the panel, and camouflaging solar panels.

Description of Related Art

Today, most of the electrical power generated that is used to light andheat homes and buildings is derived from coal, petroleum, hydro electricdams, nuclear power, wind power, ocean current power and so forth. Theelectrical power is generated at a power plant by utility companies anddelivered to end users via transmission lines and distribution lines.The electrical power is distributed within homes and businesses atusable voltages.

Most currently used techniques for generating electrical power have afuel cost. All facilities for generating electrical power have afacility cost. Further, the cost of transmission and distribution linesis substantial. Power loss during transmission of the electrical powerfrom the power plants to the end users can be substantial. As electricalpower consumption continues to increase additional facilities must beconstructed to service the increase in demand.

Fossil fuels, such as petroleum and coal that produce most electricalenergy are non-renewable. The price of these natural resources continuesto increase. In cases of hydro electric power generation, the availableelectric output depends entirely upon natural circumstances such as rainfall. For instance, during years when rainfall is low, power generationis also low, which affects the entire community who use this source ofelectrical power. Wind power is typically only available during daylighthours and fluctuates both seasonally and based upon local weatherpatterns. In the case of nuclear power, the technology is expensive,construction of power generating stations is expensive, and nuclearhazards cannot entirely be ruled out, in spite of extensive safeguards.Nuclear power generation is not available in many regions of the worldbecause of security concerns.

In addition, adverse environmental effects from all of these powergeneration methods is enormous. In other words, each of these powergeneration methods has its own adverse environmental effects such ashydro electric dams adversely affecting bio-diversity and possiblycausing floods of enormous destruction should a dam burst. The windpower generation takes huge amounts of land and may be aestheticallyunpleasant. Coal and petroleum generation causes environmentaldegradation in the form of carbon dioxide and toxic emissions, causingenormous adverse effects on natural weather cycles, having damagingeffects on life as a whole in the planet, in the long run. Similarly,nuclear waste can be hazardous; disposing nuclear waste is veryexpensive and also has the ability to have an adverse effect on theenvironment.

Solar panels, also referred to as photovoltaic panels, typically includea relatively large number of photovoltaic cells to convert solar energydirectly to electrical energy. This electrical energy is used in placeof electrical energy generated from other sources and is used to powerhomes and businesses. Solar panels are often times deployed in arraysand electrically coupled together to produce a combined electricaloutput. The solar arrays are often coupled to banks of batteries andcoupled to the electrical grid via an inverter. Excess electrical energyproduced by an array of solar panels is fed back into the utilityelectrical grid and transmitted to other users.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram illustrating the relationship between a solar panelmounted on an angled roof of a dwelling, a pedestrian observer, and thesun.

FIG. 2 is a diagram illustrating various angles of solar panel arrays atdiffering angles of orientation with respect to a horizontal reference.

FIG. 3 is an exploded view of a solar panel constructed according to oneor more embodiments.

FIG. 4 is a diagram illustrating louvers of a solar panel constructedaccording to one or more embodiments.

FIG. 5A is a diagram illustrating the path of solar insolation upon asolar panel via a louver layer according to one or more embodiments.

FIG. 5B is a diagram illustrating a solar panel that includes tiltedlouvers constructed according to one or more embodiments.

FIG. 6A is a graph illustrating street visibility index versus roofangle of a solar panel constructed according to one or more embodiments.

FIG. 6B is a graph illustrating the percentage of sunlight transmittedthrough the louvers versus solar panel angle of a solar panelconstructed according to one or more embodiments.

FIGS. 7A, 7B, 7C, and 7D are graphs illustrating the percentage ofsunlight transmitted through the louvers versus solar panel angle of asolar panel constructed according to one or more embodiments.

FIGS. 8A and 8B illustrate a prior art solar panel and a portion of asolar panel constructed according to one or more embodiments.

FIGS. 9A and 9B illustrate a prior art solar panel and a portion of asolar panel constructed according to one or more embodiments.

FIGS. 10A and 10B are photographs of a roofing tile that has mountedtherein a solar panel constructed according to one or more embodiments.

FIGS. 11A and 11B include photographs and diagrams illustrating steps indesigning solar panels for one or more dwellings according to one ormore embodiments.

FIG. 12 is an overhead view of a neighborhood having homes locatedtherein for which solar panels of the homes are designed according toone or more embodiments.

FIG. 13 are photographs illustrating views of a home having solar panelsmounted thereon that are designed and constructed according to one ormore embodiments.

FIG. 14 are photographs illustrating views of a home having solar panelsmounted thereon that are designed and constructed according to one ormore embodiments.

FIGS. 15A, 15B, 15C and 15D illustrate a top layer that is constructedof glass and that includes a saw tooth surface that obscures a view ofcovered photovoltaic cells from a low viewing angle.

FIG. 16 is a sectional side view illustrating a laminated solar panelconstructed according to one or more embodiments.

FIG. 17 is a sectional side view illustrating a coated backsheetconstructed according to one or more embodiments.

FIG. 18 is a graph illustrating the reflectance spectrum of a solarpanel constructed according to one or more embodiments.

FIG. 19 is a sectional side view illustrating a laminated solar panelconstructed according to one or more embodiments.

FIGS. 20A-20B are random patterns generated that can be used to create acamouflage film according to one or more embodiments.

FIG. 21A is a solar tile that comprises a camouflage film according toone or more embodiments.

FIG. 21B is a solar tile that does not comprise a camouflage filmaccording to one or more embodiments.

FIG. 22A-22D are solar tiles with a camouflage film according to one ormore embodiments.

FIG. 23 is a series of micrographs that show the topography of a siliconwafer.

FIG. 24 is a sectional side view illustrating a laminated backsheetaccording to one or more embodiments.

DETAILED DESCRIPTION OF THE DISCLOSURE

A number of design tradeoffs exist for solar panels. It is beneficialfor the solar panels to be efficient, inexpensive, and aestheticallypleasing, because they are installed in arrays. These arrays of solarpanels may be considered eye-sores by some observers. Residential solararrays, for example, are often mounted upon the roofs of homes and otherbuildings. When mounted on the roofs of homes, the solar panels mountparallel to the roofs. While this type of mounting technique is costeffective, the photovoltaic cells of the solar panels are visible topersons viewing the home or other structure, causing an unsightlyappearance to the home, detracting from the aesthetics of the home. Suchunsightly appearance may also violate restrictive covenants in someneighborhoods. Thus, it is desirable for the solar panels to have theappearance of roofing material with same/similar color to shingles.Further, it is desirable for the solar panels to have uniform perceivedcolor across their areas and otherwise be visually appealing. Thedisclosure below provides various techniques for improving theaesthetics and performance of solar panels.

1. Obscuring Solar Arrays from Certain Viewing Angles

FIG. 1 is a diagram illustrating the relationship between a solar panel102 (or solar panel array) mounted on an angled roof of a dwelling, apedestrian observer, and the sun. As illustrated and generally known, itis desired to have the solar panel 102 perpendicular to the angle ofincidence of the solar rays coming from the sun to maximize capturedsolar energy and convert the captured solar energy to electrical energy.A pedestrian observer of the solar array 102 may judge the solar panel102 unsightly. Further, the view of the solar panel 102 may violaterestrictive covenants or detract from the aesthetic qualities of thehome or other structure upon which the solar panel 102 mounts.

Thus, according to some embodiments, the solar panel 102 has a constructthat helps to obscure the solar panel 102 from being viewed by thepedestrian observer. In the construct of the solar panel 102, the solarpanel 102 includes one or more louver layers. The structure of such asolar panel will be described further with reference to FIG. 3 . Thelouver layer of the solar panel causes the solar panel to have asubstantially or fully solid color when viewed at a side angle, such asthe side angle of the pedestrian observer of FIG. 1 . That is, thelouver layer helps to obscure the solar panel or solar cell from viewalong certain sight lines. The louver layer optionally includes a filmthat contains the louvers.

FIG. 2 is a diagram illustrating various angles of solar panel arrays atdiffering angles of orientation with respect to a horizontal reference.Each of the solar panels 202, 204, and 206 mounts at a differing anglewith respect to the sun and the pedestrian observer illustrated in FIG.2 . According to some embodiments, the design and construction of thelouvers of the solar panels 202, 204 and 206 are based upon the angle(s)of mounting of the solar panels 202, 204, and 206. Examples of thedesign and construction process for such solar panels 202, 204, and 206will be described further herein with respect to subsequent figures.

FIG. 3 is an exploded view of a solar panel 300 constructed according tosome embodiments. The solar panel 300 includes a backsheet layer 302, abottom encapsulant layer 304 adjacent the backsheet layer 302, aplurality of photovoltaic cells 306 adjacent the bottom encapsulantlayer 304, a top encapsulant layer 308 adjacent the plurality ofphotovoltaic cells 306 having a plurality of louvers constructed thereinto block side view of the plurality of photovoltaic cells 306, and a toplayer 310 adjacent the top encapsulant layer 308.

In some embodiments, the backsheet layer 302 is constructed of glass ora barrier film. The bottom encapsulant layer 304 may be constructed ofEthylene-vinyl acetate (EVA), also known as poly(ethylene-vinyl acetate)(PEVA), which is the copolymer of ethylene and vinyl acetate. Thephotovoltaic cells 306 may be of conventional construct. In someembodiments, the top encapsulant layer 308 is a formed structure of EVAthat includes the louvers. The top layer 310 may be constructed of glassthat is textured, toughed, having low iron content and of a thicknesssufficient to protect the solar panel 300 underlying components. Theencapsulant layers can also be polyolefin encapsulant such as 3M SolarEncapsulant Film P08100N.

The top encapsulant layer 308 may include a plurality of louversdistributed across its area. The plurality of louvers may includediffering incident angles across the top encapsulant layer 308. Further,in some embodiments, a first group of the plurality of louvers have afirst incident angle and a second group of the plurality of louvers havea second incident angle that differs from the first incident angle. Inother constructs, the louvers have a number of differing incidentangles. As will be described further herein, the louvers are designed toprovide viewing obstruction to the photovoltaic cells 306 when viewedfrom a side angle but to minimally impede solar energy passed to thephotovoltaic cells 306.

The plurality of louvers may have a design color that causes the solarpanel to have the appearance of the design color when viewed from a sideangle, thereby obscuring the solar panel from view. Further, with thisconstruct, the solar panel may have the design color when viewed fromthe side angle and a differing color when viewed from other than theside angle.

With the embodiments of the solar panel described herein, it is desiredto increase the angle transparency of the louvers for solar efficiencybut to have the solar panel have the appearance of a solid color from aside angle. Various colors may be used, including gray tones from darkto light, earth tones, cedar color or appearance, and a printappearance. Thus, the top encapsulant layer 308 that includes thelouvers may be constructed not only to cause the appearance of aparticular color or colors from the side viewing angle but also aparticular pattern or design.

According to some aspects of the present disclosure, the solar panel 300may include a small vertical wall to further obscure view of thephotovoltaic cells 306 when viewed from the side. Further, the top layer310 may have a textured surface (textured glass), for example, in a sawtooth pattern. This saw tooth pattern may include a vertical wall oneach tooth that assists in obscuring the view of a covered photovoltaicpanel from a low viewing angle. Examples of this structure areillustrated further in FIGS. 15A-15D. The solar panel 300 may alsoinclude electronics or an electrical connector for coupling the solarpanel 300 to other solar panels or to other electrical connections.

FIG. 4 is a diagram illustrating louvers 402 of a solar panelconstructed according to one or more aspects of the present invention.As shown the louvers 402 are dispersed across the top encapsulant layer308. The size, shape, height, and separation of the louvers is designedto cause the solar panel to have a desired appearance from one or moreparticular side viewing angles and also to maximize the amount of solarenergy that passes through the top encapsulant layer 308, which includesthe louvers, to the photovoltaic cells 306.

FIG. 5A is a diagram illustrating the path of solar insolation upon asolar panel 500 via a louver layer 502 according to one or more aspectsof the present disclosure. As is shown, the louvers 504 are preferablydesigned and constructed to pass a maximum amount of solar energy to thephotovoltaic cells 506 and to cause the solar panel to have a desiredappearance from a side viewing angle. The design of the louvers 504 ismade to maximize performance and to meet aesthetics. Simulations mayinclude simple ray tracing and take into account refractive index of thesurface of the cell, impact of multiple reflections, and the exactposition of the sun. Approximations in the design may considerun-polarized light, full absorption by the photovoltaic cells inside thelouvers, that the simulated day is sunny and that the layers aretransparent. The louvers 504 shown in FIG. 5A may be tilted to assist ininternal collection of solar energy to increase efficiency of the solarpanel 500. The louver layer 502 may be a film that contains the louvers504.

FIG. 5B is a diagram illustrating a solar panel 510 that includes tiltedlouvers 512 constructed according to one or more aspects of the presentdisclosure. With tilted louvers 512, such as those illustrated in FIG.5A, sunlight at a low angle with respect to the solar panel is absorbedto obscure the view of the photovoltaic cells from an angle of anobserver, and the sunlight that is received at a high angle of incidenceis reflected (internally in some embodiments) by the louvers 512 ontothe photovoltaic cells 514.

FIG. 6A is a graph illustrating street visibility index versus roofangle of a solar panel constructed according to one or more aspects ofthe present disclosure. As is shown, as the roof angle approaches 90degrees, more of the photovoltaic panel is visible (louvers hide less).Further at low roof angles, the photovoltaic panels are not viewablefrom a zero-degree side view but lesser impeded from a 45-degree sideview. Parameters modeled to create these simulated results include theshape and orientation of the louvers (e.g., orthogonal louvers with 100micron spacing), the roof orientation (e.g., facing south), thegeographic location of the roof (e.g., Palo Alto, Calif.), the day, thehour, and other parameters, as well as the refractive index of thematrix and the louvers.

FIG. 6B is a graph illustrating the percentage of light transmittedthough the louvers versus solar panel angle of a solar panel constructedaccording to one or more aspects of the present disclosure. As isillustrated, these graphs consider month of the year and yearly averageof the percent of transmitted light though the top encapsulant layer,which includes the louvers, versus solar panel angle for a particularlouver design.

FIGS. 7A, 7B, 7C, and 7D are graphs illustrating the percentage of lighttransmitted through the louvers versus solar panel angle of a solarpanel constructed according to one or more aspects of the presentdisclosure. As is illustrated, these graphs consider month of the yearand yearly average of the percent of transmitted light though the topencapsulant layer, which includes the louvers, versus solar panel anglefor particular louver designs.

FIGS. 8A and 8B illustrate a prior art solar panel 800 and a portion ofa solar panel 802 constructed according to one or more aspects of thepresent disclosure. The solar panel 802 causes the photovoltaic cells tobe viewable from a close to perpendicular viewing angle in FIG. 8A andto be hidden from more of a side angle view in FIG. 8B. Contrast this tothe prior art solar panel 800 that allows the photovoltaic cells to beseen from both viewing angles.

FIGS. 9A and 9B illustrate a prior art solar panel 900 and a solar panel902 constructed according to one or more aspects of the presentdisclosure. The solar panel 902 causes the photovoltaic cells to beviewable from a close to perpendicular viewing angle in FIG. 9A and tobe hidden from more of a side angle view in FIG. 9B. Contrast this tothe prior art solar panel 900 that allows the photovoltaic cells to beseen from both viewing angles.

FIGS. 10A and 10B illustrate a roofing tile 1000 that has mountedtherein a solar panel 1002 constructed according to one or more aspectsof the present disclosure. When viewed from a substantiallyperpendicular viewing angle, the photovoltaic cells 1002 of the roofingtile 1000 are viewable in FIG. 10A. From a side angle as shown in FIG.10B, the photovoltaic cells 1002 of the roofing tile 1000 are hidden orobscured.

FIGS. 11A and 11B include photographs and diagrams illustrating steps indesigning solar panels for one or more dwellings according to one ormore aspects of the present disclosure. The first step is to make anassessment of a roof upon which solar panels will be installed. Thedwelling, in this case, is photographed and then geotagged. Data isgenerated from the photograph and the geotag, e.g., area and features,roof pitch, geographical data, and a street vantage point. The solarpanels are then designed, rendered, laid out and considered for costbased upon the generated data. The color of the roof, the type of solarpanel to be installed, the vantage point film, and other considerationsare made in the design of the solar panel. A roof kit is then generated,tempered, assembled, laminated, inspected, and shipped to the site forinstallation.

FIG. 12 is an overhead view of a neighborhood having homes locatedtherein for which solar panels of the homes are designed according toone or more aspects of the present disclosure. The neighborhood in whichthe homes are located may have restrictive covenants requiring certainroofing appearance. The solar panels may be designed to meet theserestrictive covenants and local laws and further to cause the aestheticsof the installation to be attractive.

FIG. 13 are photographs illustrating views of a home having solar panelsmounted thereon that are designed and constructed according to one ormore aspects of the present disclosure.

FIG. 14 are photographs illustrating views of a home having solar panelsmounted thereon that are designed and constructed according to one ormore aspects of the present disclosure.

FIGS. 15A, 15B, 15C, and 15D illustrate an embodiment of a top layer(e.g., top layer 310). Top layer 1500 illustrated in FIGS. 15A-15D isconstructed of glass and includes a saw tooth surface 1502 that obscuresa view of covered photovoltaic cells 1504 from a low viewing angle.Referring first to FIG. 15A, the top layer 1500 is shown to have asurface 1502 that is formed in a saw tooth pattern having vertical toothsurfaces 1502A and angled tooth surfaces 1502B. The vertical toothsurfaces 1502A are formed substantially perpendicular (approximately 90degrees) to the solar panel structure and the angled tooth surfaces1502B are formed at an angle that is between perpendicular to the solarpanel structure and parallel to the solar panel structure. In someembodiments, this angle is selected based upon the installation locationof the solar panel to cause the solar panel to be efficient while stillable to hide the photovoltaic panels from a low angle side view. Theview of FIG. 15A is a side view and the top layer 1500 is thereforesubstantially non-transparent based upon the black coloring upon thevertical tooth surfaces 1502A.

Referring next to FIG. 15B, the top layer 1500 is shown as being viewedfrom a perspective of approximately perpendicular to the solar panel.Thus, the top layer 1500 is mostly transparent from this perspectiveview.

Referring next to FIG. 15C, the top layer 1500 is shown residing upon aphotovoltaic cell layer 1504. The view of FIG. 15C is approximately fromthe same viewing angle as the view of FIG. 15B. From this viewing angle,the top layer is mostly transparent such that the photovoltaic cell 1504may be viewed through the top layer 1500.

Referring next to FIG. 15D, the top layer 1500 is shown residing uponthe photovoltaic cell layer 1504 from a view similar to that of FIG.15A. Thus, the photovoltaic cells are hidden from view based upon thestructure of the saw tooth surface of the top layer.

2. Coated Backsheet for Solar Panels

Turning now to FIGS. 16-18 , a coated backsheet for a solar panel isdescribed that reflects light in the infrared range to maintain a lowercell temperature of the solar panel while also providing low reflectionin the visible range to color match the backsheet with the cell andimprove the aesthetics of the solar panel.

In the architectural industry, physical vapor deposition (PVD) coatingsmade of alternate dielectric and metallic layers are successfully usedto reduce the heat going into buildings. According to one or moreembodiments, a new backsheet made of a coated plastic film that reflectslight in the infrared range also provides low reflection in the visiblerange.

FIG. 16 is a sectional side view illustrating a laminated solar panel1600 constructed according to one or more embodiments. The laminatedsolar panel 1600 includes a topsheet 1602, a solar cell layer 1604, anda backsheet 1606. The topsheet 1602 is made of glass in the illustratedembodiment but may be made of differing materials in other embodiments.The solar cell layer 1604 is made of EVA in the illustrated embodimentbut may be made of differing materials, such as polyolefin, in otherembodiments. The solar cell layer 1604 includes a plurality of solarcells 1605 encapsulated within the EVA material. Sunlight 1608substantially passes through the topsheet 1602 and either impacts thesolar cells 1605 or passes between the solar cells to the backsheet1606. The backsheet 1606 absorbs some of the sunlight 1608 and reflectsa portion of the sunlight.

FIG. 17 is a sectional side view illustrating a coated backsheet 1606constructed according to one or more embodiments. According to certainembodiments, layers 1704A-1704D as shown in FIG. 17 are deposited usinga PVD process on top of a substrate 1702. The backsheet panel 1606 ismade of a transparent or non-transparent substrate 1702 such as glass,EVA, polyethylene terephalate (PET), or an alloy of polyphenylene oxideand styrene (modified PPO). The substrate 1702 may or may not containabsorbing material to cause it to have a black (or any other) color. Onthat substrate 1702 is applied a thin coating made of n+1 dielectricmodules (1704A, 1704B, 1704C, and 1704D, also referred to as dielectriclayers) and n metallic layers (1706A, 1706B, and 1706C), n being aninteger (e.g., 1, 2, or 3). A coating of 2n+1 layers is applied asfollows: dielectric module/metallic layer/dielectric module/metalliclayer . . . /dielectric module/substrate, each metallic layer beingbetween two dielectric modules and the substrate being in contact with adielectric module. In some embodiments, the number of layers differsfrom the illustrated embodiments.

In some embodiments, a dielectric module is a transparent material madeof one or several layers of nitrides or oxides of the elements Si, Al,Ti, Zn, Sn, Nb, In, Zr, or any combination of those elements. Forexample, 3 nm of Si₃N₄ material is a dielectric module, and a stack of30 nm of Si₃N₄ and 10 nm of Zinc Aluminum oxide is also a dielectricmodule. A dielectric module thickness is preferably between 10 nm and100 nm.

In some embodiments, a metallic layer is made of one or several layersof Ni, Cr, Fe, Nb, Ti, Cu, Al, Ag, Au, Pt, or any combination of thosemetals. For example, a layer of Nb is a metallic layer. A layer of Nbwith Ni and Cr layers above or below the Nb layer is also a metalliclayer. A metallic layer thickness is preferably between 4 nm and 40 nm.

According to certain embodiments of the present disclosure, thebacksheet has different characteristics depending on the specific layersthat are deposited using PVD. For example, a deposited layer of Si₃N₄can provide an efficient barrier to alkaline ions such as Na+. Further,depositing a conductive layer as one of the layers in the backsheetcoating can be used to enhance electrostatic properties. In someembodiments, one or more of the deposited layers that comprise thebacksheet is electrically conductive and can be used as part of theenergy harvesting mechanism. Specific structure or circuitry within thatlayer can be created by depositing the layer using PVD and subsequentlylaser etching away conductive material to create tracks (or circuitry).According to some embodiments, the layers that are formed using PVDcause the backsheet to absorb light in the visual range, which aids incolor matching of the backsheet to cell 1605. In some embodiments, thedeposited layers are chosen to provide low overall radiation absorption(high reflection) while keeping low reflectance in the visible range, toyield desirable color matching to the cell while maintaining a lowercell temperature (e.g., providing less heat to the cell compared to sometraditional backsheets) thereby increasing cell efficiency and energygeneration.

FIG. 18 is a graph illustrating the reflectance spectrum of a solarpanel constructed according to one or more embodiments. The embodimentresulting in the spectrum of FIG. 18 may be constructed as follows:

Layer Thickness Si3N4 66.7 nm Nb 25.1 nm Si3N4 14.2 nm SiO2 38 nm TiO218 nm PET substrate 0.5 mm

In the reflectance spectrum of FIG. 18 , the reflectance is higher forinfrared wavelengths compared to wavelengths in the visible range, thusgiving high performance of low visible reflectivity and high energyreflectivity. Total solar reflectance (ISO9050) is 28% (compared to 6%for a black sheet). The visible colors for D65 CIE 1934 at 60 degreesincidence is L*=55, a*=1, b*=−6 (giving a purple color matching thecell). For comparison a white backsheet would have L*>70, not matchingthe cell.

In some embodiments, a coating is obtained by PVD with commerciallyavailable equipment, for example in a roll-to-roll process. For example:Si₃N₄ can be obtained by reactive sputtering of a Si target in a plasmamade of argon and nitrogen; TiO2 can be obtained by sputtering of aTiO_(x) target in argon; SiO₂ can be obtained by sputtering of a Sitarget in O₂, Ar plasma; and Nb layer can be obtained by sputtering of aNb target in Ar plasma.

This PVD coating technology is well known for architectural coatings.Optional functionalities to the backsheet include electricity conductionfor energy harvesting. This can be obtained by laser etching of tracksinside the film, which is already conductive. The Si₃N₄ layer used insome exemplary coatings is an efficient barrier to alkaline ions such asNa+. In some embodiments, the conductive nature of the film has goodelectrostatic properties.

3. Solar Cell Camouflage Structures

Turning now to FIGS. 19-24 , techniques are described to obscure solarpanels from view through specialized construction of patternedcamouflage films, textured backsheets, and colored backsheets.

FIG. 19 shows a sectional side view that illustrates a solar cell 1900.The solar cell 1900 shown in FIG. 19 comprises a silicon wafer 1906 thatacts as the photovoltaic material. On top of the silicon wafer 1906 istypically a polymer front sheet 1904 and on top of the polymer frontsheet 1904 a glass layer 1902 (e.g., a topsheet). The glass layer 1902may comprise amorphous silica. The glass layer 1902 may also compriseother transparent materials. In some embodiments, the solar cell 1900 isobscured in such a manner that an observer finds it difficult to see thesolar cell 1900 and the solar cell 1900 blends into the background, orlooks similar to the surrounding environment. FIG. 21B illustrates asolar cell 2108 that does not blend into the surrounding roofing tile2110 (together referred to as a solar tile 2106). The solar cell 2108 isobservable towards the center of each roofing tile 2110. Solar cells mayuse other photovoltaic material beside a silicon wafer and would stillbenefit from the obscuring and camouflage techniques described herein.

This disclosure describes ways to obscure or camouflage the solar cellsfrom view by making them blend into the surrounding environment and/orobscure the silicon wafer from view. According to some embodiments, asystem uses patterned coatings that camouflage the solar cell.

A. Patterned Coating to Camouflage the Solar Cell

The solar cells may be camouflaged from view by causing them to blendinto the remainder of the solar tile using a camouflage pattern. Thiscamouflage pattern includes a thin transparent coating that ispatterned. The pattern includes blocks of a specific shape (such as asquare, a rectangle, a circle, or an arbitrary shape). For example, thecamouflage shape may comprise squares that are darker than the lightestcolor observed when observing the solar cell. This pattern of squares(or other geometries) may be randomly distributed around the area of thesolar cell. In some embodiments, the coating allows light transmissionfor the solar spectrum greater than 50%, but is slightly reflective(reflection for the solar spectrum between 1 and 20%). That is, thecoating reflects a portion of the solar spectrum that the photovoltaicmaterial may absorb.

The random pattern of shapes (squares or other shape) may be generatedusing an Ising model utilizing the Metropolis algorithm. Specifically,Metropolis dynamics may be applied around the critical temperature togenerate images having good scale invariance properties that aresuitable for obscuring and camouflaging the solar cells. However, othermethods such as random spatial processes, Gaussian random fields (e.g.,a field generated using a Hurst spectral distribution law), or use ofnatural patterns such as stone pictures may be used to obtain both smallscale and large scale features to make obscure the solar cell. FIG. 20Ashows an output obtained using an Ising model utilizing the Metropolisalgorithm. FIG. 20B shows an embodiment of a Gaussian field. Theserandom patterns have the advantage that they look natural andnon-repetitive. Optionally, colors of tiles and patterns can be variedfrom tile to tile to give a more natural appearance.

This random pattern may be used to generate a coating with a similarpattern. Depending on the specific parameters, for example, the size andshape of the object, different patterns may result.

The coating itself comprises one or more layers of material applied insome area, preferentially between 10% and 90% of the total area of thesolar cell, to a transparent substrate, such as glass or a polymer sheetsuch as PET. The layers may be deposited to the transparent substrate,using PVD or another technique known to persons of skill in the art. ThePVD or other technique must be able to form the required coatingthickness and be compatible with the materials in the coating. Forexample, Ti, Zn, Si, Al, Sn, In, Cu, Zr, Nb, or Sb oxides or nitridesmay be used as one or more of the layers formed on the substrate. Otherlayers may consist of metals such as Nb, Ag, Cu, Fe, Cr, Ni, Al, or Tialone or in combination. An exemplary coating comprises 50 nm of Si₃N₄applied on glass or PET by reactive sputtering of a Si target in aplasma containing Ar and N₂, such as widely used in PVD. Preferentialdeposition may be obtained using a mask (or other techniques known inthe art). For example, the mask may be a sheet of Kapton® containing thespecific pattern that is to be deposited. Other techniques that may beused to create the deposited pattern include photolithography orprinting techniques. For example, an organic (e.g., organic polymer)with a negative pattern may be printed at the surface of glass. Thepolymer may act as a mask for a layer coated using PVD (or anothertechnique). The organic may then be removed, by for example, burning thematerial in an oven to remove it. In some embodiments, the coating isachieved by sublimation printing or other ink printing technique.

The coating may be in the form of a film applied to the glass layer 1902(either the front or the back) of FIG. 19 or the frontsheet layer 1904(either the front or the back) of FIG. 19 . The coating may also bedirectly printed onto either the glass or frontsheet. Alternatively, thecoating may comprising a separate layer that is above the silicon wafershown in FIG. 19 .

FIG. 21A shows an example of a coating with a camouflage pattern that isapplied to the solar cells 2102, according to embodiments of the presentdisclosure. The camouflage pattern obscures the solar cells 2102 fromthe surrounding material and makes the solar tile 2100 appear to be moreuniform in appearance (e.g., it is difficult to observe where thetraditional roofing material 2104 stops and the solar cell 2102 begins).FIG. 21B illustrates solar cells 2108 without a camouflage film. Thesolar cells 2108 are visible (towards the middle of each solar tile2106).

In certain embodiments, a textured substrate may be used to furtherenhance the obscuring effects of the patterned film. FIGS. 22A-22Dillustrate exemplary camouflage coatings formed on a textured substrateaccording to certain embodiments of the present disclosure. Thetexturing may comprise raised or depressed lines in a certain direction,raised or depressed square patterns, pebbling, or other texturing.

B. Backsheet with Cell Color Matching

Another way to obscure the cells within the solar tiles is by matchingthe backsheet color to the silicon wafer of the photovoltaic and/orcreating a textured backsheet, according to certain embodiments of thepresent disclosure.

In some embodiments, the silicon wafer surface includes a pyramidaltopography. FIG. 23 illustrates the microstructure of the siliconsurface in a series of electron micrographs. The pyramidal topographymay result when the silicon (e.g., Si(111)) surface is the exposed face.The topography of the silicon surface may be different if a differentsilicon surface, such as the Si(110) or the Si(100) surface is exposed.Similarly, the topography may be different if the photovoltaic comprisedanother semiconductor, such as gallium nitride, gallium arsenide,gallium phosphide, or another semiconductor.

According to some embodiments of the present disclosure, the backsheetcomprises a textured polymer layer, such as PET, Polycarbonate, oranother suitable polymer. The textured polymer layer may have apyramidal topography, similar to the structures exhibited in the Si(111)surface shown in FIG. 23 . A coating may then be applied to the top ofthe textured polymer layer. In some embodiments, the coating layer has asimilar color (or array of colors) compared to the cell (or specificallythe silicon wafer or photovoltaic). The result of the coating/film ontop of the polymer backsheet is a film that matches the very complexcolor behavior observed when looking at a traditional cell and siliconwafer. If the topography of the silicon is different, for example, itcontains cubic features, then the backsheet may comprise similarfeatures (instead of pyramidal features). In certain embodiments, thebacksheet may comprise a glass or other transparent material that neednot be a polymeric material.

A textured polymer (such as PET) backsheet may be synthesized using anumber of techniques. For example, a textured backsheet can besynthesized using a polymer injection method in which a master mold isfirst created. Using such a method, a master mold is created. Thismaster may be a metal master formed by taking a metal blank and thenlaser cutting (or otherwise forming, such as through etching) thedesired features into the metal blank. For example, pyramidal featuresmay be laser cut or otherwise formed in the metal blank. Alternatively,the master may be a glass master formed by laser cutting or using otherdeposition or etching techniques, such as electroforming. The master mayalso be formed according to other techniques known to persons of skillin the art. The resulting master will contain a negative impression ofthe features, for example a pyramidal feature in the resulting film willappear as a pyramidal pit in the master.

According to certain embodiments, other mold “parents” may be createdwith both positive and negative impressions in order to allow for thefurther creation of additional masters that will be used to produce thetextured polymer backsheet. That is, a “parent” mold that contains thenegative impression of the features may be used to create one or more“other parent” molds with positive impressions of the features to beformed in the textured polymer backsheet. The one or more “other parent”molds with the positive impressions may be used to create one or morenegative master molds that are then used to form the textured polymerbacksheet. Creating “parent” and “other parent” molds is desirable incertain instances because they allow for the creation of other mastermolds that are used to form the textured polymer backsheet, which may benecessary if a master mold is lost, or the features deteriorate fromuse. Additional master molds may also be created when increasingproduction.

After a master mold has been created, it may be used to form thetextured polymer backsheet. For example, the master mold may be used aspart of a polymer-injection-molding process to form the textured polymerbacksheet. The master mold may be inserted into an enclosure (forexample a die) and molten polymer (or other material) poured into thedie and allowed to dry. The textured backsheet will have the positivefeatures, such as pyramidal features, similar to the silicon shown inFIG. 23 . The textured polymer backsheet may be tested for qualitystandards.

In some embodiments, polydimethylsiloxane (PDMS) soft lithography may beused to create the master molds and the textured polymer backsheet.Other fabrication techniques may be used to create the mater mold andtextured polymer backsheet. In some embodiments, the resulting texturedpolymer backsheet contains the desired surface features (e.g., surfacefeatures that match the surface topography of the glass surface). Incertain embodiments, instead of a polymer (such as PET) backsheet, glass(silica or another transparent material) is used as the backsheetsubstrate.

The backsheet substrate (textured or otherwise) may be coated with oneor more layers to create a specific color profile that helps to visuallyobscure the cell, and specifically the silicon wafer (or wafer formed ofother semiconductor material) of the photovoltaic cell. The coating ontop or on the bottom of the backsheet substrate may consist of one ormore layers. The entire surface of the backsheet substrate need not becoated. Optionally, the total surface area of the backsheet substrate iscoated between 10% to 90%. The coating layers may be formed with PVD oranother technique known to persons of skill in the art. The PVD or othertechnique forms the required coating thickness and is compatible withthe materials in the coating. For example, Ti, Zn, Si, Al, Sn, In, Cu,Zr, Nb, Sb oxides or nitrides may be used as one or more of the layersformed on the backsheet substrate. Other layers may include metals suchas Nb, Ag, Cu, Fe, Cr, Ni, Al, Ti alone or in combination. For example,FIG. 24 illustrates coating layers 2400 (TiO₂), 2402 (Al), and 2404(TiO₂) according to certain embodiments. The TiO₂/Al/TiO2 layers (in thethicknesses shown in FIG. 24 , specifically, 100 nm/4 nm/5 nm) produce apurplish color. In some embodiments, the coating includes a layer of Sion the substrate and either a layer of indium tin oxide (ITO) on the Silayer (e.g., substrate/Si/ITO) or a layer of Si₃N₄ on the Si layer(e.g., substrate/Si/Si₃N₄). Optionally, the entire backsheet istextured. In some embodiments, the textured backsheet is used to mimican actual wafer (e.g., to act as a fake wafer with the same color as theactual wafer). The coating layers may comprise silicone based coatingsor solvent based ink systems.

Pattern coatings, pattern coatings over a textured substrate, a texturedbacksheet, and a coated backsheet may all be used together to helpobscure the solar cell from view and cause it to blend into itsenvironment (such as the rest of the solar tile), thereby obscuring orcamouflaging the solar cell.

The foregoing disclosure is not intended to limit the present disclosureto the precise forms or particular fields of use disclosed. As such, itis contemplated that various alternate embodiments and/or modificationsto the present disclosure, whether explicitly described or impliedherein, are possible in light of the disclosure. Having thus describedembodiments of the present disclosure, a person of ordinary skill in theart will recognize that changes may be made in form and detail withoutdeparting from the scope of the present disclosure. Thus, the presentdisclosure is limited only by the claims.

In the foregoing specification, the disclosure has been described withreference to specific embodiments. However, as one skilled in the artwill appreciate, various embodiments disclosed herein can be modified orotherwise implemented in various other ways without departing from thespirit and scope of the disclosure. Accordingly, this description is tobe considered as illustrative and is for the purpose of teaching thoseskilled in the art the manner of making and using various embodiments ofthe disclosed system, method, and computer program product. It is to beunderstood that the forms of disclosure herein shown and described areto be taken as representative embodiments. Equivalent elements,materials, processes or steps may be substituted for thoserepresentatively illustrated and described herein. Moreover, certainfeatures of the disclosure may be utilized independently of the use ofother features, all as would be apparent to one skilled in the art afterhaving the benefit of this description of the disclosure.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any contextual variants thereof, areintended to cover a non-exclusive inclusion. For example, a process,product, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements, but may include otherelements not expressly listed or inherent to such process, product,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition “A or B” is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B is true (orpresent).

Although the steps, operations, or computations may be presented in aspecific order, this order may be changed in different embodiments. Insome embodiments, to the extent multiple steps are shown as sequentialin this specification, some combination of such steps in alternativeembodiments may be performed at the same time. The sequence ofoperations described herein can be interrupted, suspended, reversed, orotherwise controlled by another process.

It will also be appreciated that one or more of the elements depicted inthe drawings/figures can also be implemented in a more separated orintegrated manner, or even removed or rendered as inoperable in certaincases, as is useful in accordance with a particular application.Additionally, any signal arrows in the drawings/figures should beconsidered only as exemplary, and not limiting, unless otherwisespecifically noted.

What is claimed is:
 1. A solar panel comprising: a topsheet; aphotovoltaic layer adjacent the topsheet, the photovoltaic layercomprising a plurality of photovoltaic cells encapsulated in aphotovoltaic layer material, the plurality of photovoltaic cellscomprising a first topography; and a textured layer comprising a secondtopography matching the first topography; and a layer of Si coating asurface of the textured layer facing the photovoltaic layer, wherein acolor of the textured layer coated by the layer of Si matches a color ofthe plurality of photovoltaic cells.
 2. The solar panel of claim 1,wherein the textured layer comprises polyethylene terephalate.
 3. Thesolar panel of claim 1, wherein the textured layer comprises glass. 4.The solar panel of claim 1, wherein the textured layer further comprisesa layer of indium tin oxide (ITO) or Si₃N₄ on the layer of Si.
 5. Thesolar panel of claim 4, wherein the textured layer is formed using amolding process.
 6. The solar panel of claim 1, wherein the texturedlayer is a backsheet.
 7. The solar panel of claim 1, wherein thephotovoltaic layer comprises silicon with the first topography that hasfeatures of a first shape and the textured layer comprises a polymerthat has the second topography with features of the first shape.
 8. Thesolar panel of claim 1, wherein the first topography has pyramidalfeatures and the second topography has matching pyramidal features andwherein the textured layer is formed of a polymer.
 9. The solar panel ofclaim 1, wherein the textured layer comprises metallic layers and etchedtracks that form electrical circuitry.
 10. A solar panel comprising: aphotovoltaic layer comprising a plurality of photovoltaic cellsencapsulated in a photovoltaic layer material, the plurality ofphotovoltaic cells comprising a first topography; a topsheet positionedon a first side of the photovoltaic layer; and a textured layercomprising a second topography that matches the first topography; and alayer of Si coating the textured layer, wherein the textured layerreflects light matching a color of the plurality of photovoltaic cellsand the textured layer is positioned on a second side of thephotovoltaic layer opposite the first side.
 11. The solar panel of claim10, wherein the reflectance of the textured layer is higher for infraredwavelengths than for visible wavelengths.
 12. The solar panel of claim10, wherein the topsheet is a layer of glass.
 13. The solar panel ofclaim 10, wherein the textured layer comprises a polymer.
 14. The solarpanel of claim 10, wherein the second topography comprises pyramidalfeatures.
 15. The solar panel of claim 10, wherein the photovoltaiclayer material further comprises ethylene vinyl acetate (EVA).
 16. Thesolar panel of claim 10, wherein the layer of Si coated on the texturedlayer is covered by a layer of indium tin oxide (ITO) or Si₃N₄.